Authors:

Richard Register
(Princeton University)

Sheng Li
(Princeton University)

Recent developments in coordinative chain transfer polymerization have
enabled the synthesis of ethylene-co-octene block copolymers, where the
blocks are either crystallizable (an ethylene-co-octene random copolymer
block with low octene content) or amorphous (analogous block with high
octene content). With a suitable choice of catalyst type(s) and reactor
train configuration, accessible chain architectures include diblock, where
each block ideally has the most-probable distribution of chain lengths, and
multiblock, where both the individual blocks and the number of blocks per
chain follow the most-probable distribution. With a sufficiently large
interblock octene differential, block copolymers of both architectures,
containing roughly equal masses of the two types of block, self-assemble in
the melt into well-ordered lamellar structures, despite the large
polydispersity. Interblock mixing, induced by the modest Flory interaction
parameter and the broad distribution of block lengths, yields an enormous
domain spacing (\textgreater\ 100 nm) despite the relatively low average
block molecular weights (\textless\ 50 kg/mol). Extensive interblock mixing
also allows the polyethylene crystals to grow freely and nearly
isotropically across the domain interfaces, while preserving the domain
structure present in the melt; in the solid state, the optical and x-ray
contrasts between dissimilar domains are greatly enhanced due to their
different levels of crystallinity. (Work conducted in collaboration with
Jeffrey Weinhold, Philip Hustad, and Brian Landes of Dow Chemical Core
R{\&}D.)

To cite this abstract, use the following reference: http://meetings.aps.org/link/BAPS.2013.MAR.J11.4